The present invention relates to an improved sub-surface, or in-ground/in-water, direct expansion heat pump system incorporating a unique combination of various design feature improvements, component strengthening criteria, air handler sizing, sub-surface vertical heat exchange design improvements, sub-surface near horizontal long trench designs, pin restrictor sizing criteria, insulation criteria improvements, and sub-surface heat exchange tubing containment pipe types and lengths for use in association with any direct expansion heating/cooling system, and particularly for use with a Deep Well Direct expansion (herein referred to as a “DWDX”) system and a Long Trench Direct expansion (herein referred to as a “LTDX”) system. A DWDX system is herein defined as a direct expansion system (also periodically referred to as a “direct exchange system” in the trade) which utilizes sub-surface heat exchange tubing in excess of 100 feet deep. The present invention may also be utilized in any direct expansion systems 100 feet, or less, in depth (near surface) with improved operational efficiency results. A LTDX system is herein defined as a direct expansion system which utilizes sub-surface heat exchange tubing installed in a near horizontal fashion at depths of less than 50 feet. Typically, LTDX systems will be installed at depths ranging from between 3 feet and 15 feet deep.
Ground source/water source heat exchange systems typically utilize fluid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged tubing. Water-source heating/cooling systems typically circulate, via a water pump, water, or water with anti-freeze, in plastic underground geothermal tubing so as to transfer heat to or from the ground, with a second heat exchange step utilizing a refrigerant to transfer heat to or from the water, and with a third heat exchange step utilizing an electric fan to transfer heat to or from the refrigerant to heat or cool interior air space.
Direct eXpansion (herein referred to as “DX”) ground source systems, where the refrigerant transport lines are placed directly in the sub-surface ground and/or water, typically circulate a refrigerant fluid, such as R-22, in sub-surface refrigerant lines, typically comprised of copper tubing, to transfer heat to or from the sub-surface elements, and only require a second heat exchange step to transfer heat to or from the interior air space by means of an electric fan. Consequently, DX systems are generally more efficient than water-source systems because of less heat exchange steps and because no water pump energy expenditure is required. Further, since copper is a better heat conductor than most plastics, and since the refrigerant fluid circulating within the copper tubing of a DX system generally has a greater temperature differential with the surrounding ground than the water circulating within the plastic tubing of a water-source system, generally, less excavation and drilling is required, and installation costs are generally lower with a DX system than with a water-source system.
While most in-ground/in-water heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Various such design improvements are taught in U.S. Pat. No. 5,623,986 to Wiggs; in U.S. Pat. No. 5,816,314 to Wiggs, et al.; in U.S. Pat. No. 5,946,928 to Wiggs; in U.S. Pat. No. 6,615,601 B1 to Wiggs; in Wiggs' U.S. patent application Ser. No. 10/073,513; in Wiggs' U.S. patent application Ser. No. 10/127,517; in Wiggs' U.S. patent application Ser. No. 10/251,190; in Wiggs' U.S. patent application Ser. No. 10/335,514; in Wiggs' U.S. patent application Ser. No. 10/616,701, and in Wiggs' U.S. patent application Ser. No. 10/757,265, the disclosures of which are incorporated herein by reference.
In DX applications, supply and return refrigerant lines may be defined based upon whether they supply warmed refrigerant to the system's compressor and return hot refrigerant to the ground to be cooled, or based upon the designated direction of the hot vapor refrigerant leaving the system's compressor unit, which is the more common designation in the trade.
For purposes of this present invention, when applicable, the more common definition will be utilized. Hence, supply and return refrigerant lines are herein defined based upon whether, in the heating mode, warmed refrigerant vapor is being returned to the system's compressor, after acquiring heat from the sub-surface elements, in which event the larger interior diameter, sub-surface, vapor/fluid line is the return line and evaporator, and the smaller interior diameter, sub-surface, liquid/fluid line, operatively connected from the interior air handler to the sub-surface vapor line, is the supply line; or whether, in the cooling mode, hot refrigerant vapor is being supplied to the larger interior diameter, sub-surface, vapor fluid line from the system's compressor, in which event the larger interior diameter, sub-surface, vapor/fluid line is the supply line and condenser, and the smaller interior diameter, sub-surface, liquid/fluid line is the return line, via returning cooled liquid refrigerant to the interior air handler, as is well understood by those skilled in the art. In the heating mode the ground is the evaporator, and in the cooling mode, the ground is the condenser.
As taught by Wiggs in the above-said patents and/or patent applications, an improved means of designing a DX system for a reverse-cycle heating/cooling system operation consists of insulating only one smaller interior diameter, sub-surface, line, designed primarily for liquid/fluid refrigerant transport, which smaller line may be utilized as a supply line in the heating mode and as a return line in the cooling mode, and of not insulating at least one, or two or more combined, larger interior diameter, sub-surface, lines, designed primarily for vapor/fluid transport, which can provide expanded surface area thermal heat transfer as return lines in the heating mode and as supply lines in the cooling mode. This design improvement applies to any DX system, including a DWDX system and a LTDX system. While at least two, larger combined interior diameter, vapor/fluid refrigerant transport lines, operatively connected to one, smaller interior diameter, liquid/fluid refrigerant transport line would generally be preferable because of the resulting expanded, and spaced apart, heat transfer surface contact area, instances may arise where only one, larger interior diameter, vapor/fluid refrigerant line, operatively connected to one, smaller interior diameter, liquid/fluid-refrigerant line could also be preferable, or where a larger interior diameter vapor/fluid refrigerant line is spiraled around a centrally located, insulated, smaller diameter liquid/fluid refrigerant line could be preferable.
Where a close to zero-tolerance short-circuiting effect is desirable, and where the time and expense of constructing other designs, such as a concentric tube within a tube, or a spiraled single fluid return line and single fluid supply line of the same sized interior diameters, could be financially, or functionally and/or efficiently, prohibitive in a deep well direct expansion application, and where the thermal exposure area of a single geothermal heat transfer line, or tube, could be too centralized and too heat transfer restrictive, a system design improvement would be preferable which incorporated a cost-effective installation method, capable of operating in a reverse-cycle mode in a sub-surface direct expansion application, with close to zero-tolerance short-circuiting effect, with expanded sub-surface heat transfer surface area capacities, and with a liquid refrigerant trap means at the bottom of the sub-surface heat exchange lines to assist in preventing refrigerant vapor migration, from the refrigerant vapor line into the refrigerant liquid line, as is taught in Wiggs' pending U.S. patent application Ser. No. 10/251,190, which is incorporated herein by reference.
Virtually all heat pump systems, including direct expansion heat pump systems, utilize a compressor, an interior heat exchange means, an exterior heat exchange means, thermal expansion devices, an accumulator, a receiver, and refrigerant transport tubing. Generally, most direct expansion systems are designed to utilize, and utilize, conventionally sized equipment components, as explained in Wiggs' U.S. patent application Ser. No. 10/757,265, which is incorporated herein by reference. For example, a three ton conventional direct expansion system, designed to accommodate a three ton heating/cooling load as per ACCA Manuel J load calculations or other similar design criteria, typically utilizes a 3 ton compressor, a 3 ton air handler (a common interior heat exchange means), a 3 ton design capacity sub-surface heat exchange means (often about 5 horizontal 100 foot long ¼″ diameter refrigerant grade copper tubes per ton, a 3 ton metering device (typically one self-adjusting thermal expansion valve for each of the cooling and heating segments), a 3 ton accumulator, a 3 ton receiver (with various other receiver designs, claimed or utilized, based upon about a 50% greater to a 50% smaller size of the compressor tonnage size utilized, as explained in U.S. Pat. No. 5,946,928 to Wiggs, which is incorporated herein by reference), and standard 3 ton design refrigerant transport tubing (such as a ⅜″ diameter refrigerant grade copper liquid/fluid transport line and a ⅞′ diameter refrigerant grade copper vapor/fluid transport line) to and from the compressor unit, the heat exchange means, and the other system components.
An improved design for conventional near-surface and other direct expansion heating/cooling systems is also taught in the said U.S. Pat. No. 5,946,928 to Wiggs. Conventional direct expansion systems typically require a relatively large surface area of land within which to bury an array of heat exchange tubing. While for new residential construction on relatively large lots, such designs can be well suited, the large surface area excavation requirements are often not well suited for retrofit applications, and are usually not well suited for most commercial applications, due to restricted available land surface areas.
To overcome such conventional direct expansion system application shortcomings, various designs have been developed to permit the installation of sub-surface heat exchange tubing in sub-surface tubing installed at depths of 100 feet, or more, such as those designs taught by Wiggs in various of the above-referenced patents and patent applications. However, a means to install a highly efficient DX system without having to incur drilling expenses, while permitting sub-surface heat exchange tubing to be located around the perimeter of a property, for example, rather than taking up a large portion of the entire yard area utilizing a matrix of heat exchange tubing requiring about 500 square feet or more per ton of design capacity, can also be advantageous. Thus, it is an objective of this subject invention to both disclose various design improvements for a DWDX system, for DX systems in general, and to disclose means of installing improved DX system designs in conjunction with a near surface LTDX geothermal heat exchange system
The present invention provides solutions to these preferable objectives, as hereinafter more fully described.